MICROCRYSTALLINE CELLULOSE EXTRACTED FROM COFFEE HUSKS FOR FOOD APPLICATIONS

Agro-industrial residues are excellent raw materials for obtaining food ingredients
such as cellulose, due to their renewability, non-toxicity, abundance and biodegradability. Nowadays, there has been intense biomass exploitation to obtain
sustainable processes, although residues from relevant production processes, such
as coffee, have been little investigated. Taking into account that approximately 10,800 tons were produced in 2019 and half of the mass of coffee beans is waste, the urgency to reuse these materials is undeniable. Furthermore, based on increased worldwide environmental awareness, replacing conventional extraction methods that still require hazardous (e.g., sulfuric acid) and predominantly undesirable chemicals for food ingredients is a gap to be filled. Therefore, the aim of this research was to develop a method capable of isolating cellulose by applying a combination of alkaline pretreatment and bleaching followed by hydrolysis with more environmentally friendly acids (citric, butyric, tartaric and phosphoric) than the control (sulfuric). After extraction, the cellulose was characterized and compared with commercial-grade microcrystalline cellulose (AVICEL PH101®). All samples had an increase of more than 40% in cellulose content, indicating the efficiency of the pre-treatment combination applied in the removal of amorphous structures (hemicellulose and lignin). Furthermore, regardless of the type of acid applied, the materials obtained were considered microcrystalline cellulose, in a state of transition from cellulose I to cellulose II. FTIR spectroscopy revealed similar spectra both for all extracted pulps (regardless of the acid applied in the hydrolysis) and for AVICEL PH101®, indicating that the combination of pretreatment with hydrolysis with organic acids was significantly similar to hydrolysis with sulfuric acid in coffee. Undoubtedly, the proposal developed in this research emerges as a more environmentally friendly alternative for the extraction of microcrystalline cellulose and its derivatives. The characteristics presented by microcrystalline celluloses also showed an extensive ability to act in the food industry as stabilizers in Pickering emulsions or self-assembled structures.